Jordan has asked the United States for manned surveillance aircraft to help it prevent the Syrian conflict spilling across the border, according to a top US military officer.

General Martin Dempsey, chairman of the Joint Chiefs of Staff, received the request Wednesday during his visit to Jordan. If granted, it would further boost US military support to Jordan after Washington decided to station F-16 aircraft and Patriot missiles there.

Dempsey said Jordan was interested in what the US could do to help it secure its long border with Syria, and wanted help to better integrate different sources of intelligence.

When asked what else the UScould do to better back it up, Jordan raised the provision of manned "intelligence, surveillance and reconnaissance" aircraft among other items.

"There's a process that we have for those kind of formal requests and I'll take it back with me to Washington," Dempsey said.

An influx of more than a half a million refugees from Syria has created a big problem for Jordan, forcing it to appeal for international help.

Jordan is Dempsey's last stop on a Middle East tour that started Monday in Israel.